1. Field of the Invention
One embodiment of the present invention relates to a semiconductor device. Further, one embodiment of the present invention relates to a semiconductor memory device.
2. Description of the Related Art
In recent years, semiconductor devices each including a memory circuit in which data can be written and erased and the data can be retained for a certain period have been developed.
As examples of the above semiconductor device, a dynamic random access memory (also referred to as a DRAM) (for example, see Patent Document 1) and a static random access memory (also referred to as an SRAM) (for example, see Patent Document 2) can be given.
A DRAM disclosed in Patent Document 1 is provided with a memory cell including one transistor and one capacitor. The DRAM disclosed in Patent Document 1 retains data by turning the transistor on and accumulating electric charge in the capacitor.
An SRAM disclosed in Patent Document 2 is provided with a memory cell including six transistors.